Transport in microstructures in the microwave and millimeter-wave regime

This report summarizes the work performed during a 3-year URI program on Transport in Microstructures in the Microwave and Millimeter-Wave Regime. It describes significant achievements in both basic investigations of transport physics and in applications to high-speed electronics and optoelectronics. Fundamental advances were made in measurements of transport in semiconductors under high-field conditions. A variety of ultrafast optical and optoelectronic techniques were used to perform the most comprehensive experimental study to date of the dynamics of high-field transport in semiconductors, including the first observations of the ballistic acceleration of electrons, of field-dependent velocity overshoot, and of the dynamics of impact ionization. Carrier dynamics in low-temperature-grown (LT) semiconductors and high-critical-temperature superconductors were investigated, and optimum materials growth conditions determined. The work on LT GaAs led to significant advances in high speed electronic measurement, including electro-optic network analysis up to 300 GHz bandwidth, and novel photoconductive probes with ps response, high spatial resolution, and microvolt sensitivity. LT GaAs MSM photodetectors were developed with bandwidths up to 375 GHz and both high sensitivity and large-signal capability, representing significant improvements over the prior state of the art. Novel femtosecond lasers were developed. This made possible the development of new high speed measurement techniques.